According to the latest determinations issued by the U.S. Department of Energy (DOE), ASHRAE Standard 90.1-2019 would achieve greater energy efficiency in commercial buildings compared to the previous edition (2016) of the standard. National savings were approximated at:

  • 4.7% site energy 
  • 4.3% source energy 
  • 4.3% energy cost 
  • 4.2% carbon emissions

 

DOE also issued a determination that the ICC's 2021 International Energy Conservation Code (IECC) would achieve greater energy efficiency in residential buildings compared to the previous edition (2018) of the model code. National savings were approximated at: 

  • 9.38% site energy savings
  • 8.79% source energy savings
  • 8.66% energy cost savings
  • 8.66% carbon emissions

 

The DOE determinations verify the incremental improvement in energy performance and carbon emission reductions set by these model documents. However, the latest figures by DOE may also indicate a "leveling off" of building performance improvement through energy conservation measures alone.

 

The net-zero time horizon drifts

While these improvements in energy performance mark a step forward, the latest DOE determinations suggest a extended trajectory of both model documents toward a net-zero site energy minimum standard. After the previous round of DOE determinations, the trajectory of Standard 90.1 and IECC toward setting a net-zero site energy minimum standard was approximated to be 2035 and 2037 respectively. 

The latest figures suggest a revised trajectory by which both model documents will set net-zero site energy as a minimum by approximately 2040.

 

Figure 1: National average percent reduction in predicted energy use intensity (pEUI) set by ASHRAE Standard 90.1 and the IECC relative to the 2003 CBECS (which uses building data recorded in 2000). The AIA 2030 Commitment target of achieving a 100% reduction in pEUI by 2030 is indicated. Figure by Daniel Overbey.

 

State-by-state energy code adoption has a long way to go

While ASRAE and ICC continue to advance their model standard and code on a regular update cycle, state-by-state adoption is much more varied and less predictable. 

DOE regularly updates its State Code Adoption Tracking Analysis resource, which includes each state's modeled site energy index relative to current "model codes" (i.e., ASHRAE 90.1-2019 and 2021 IECC). By charting each state's standing in both the commercial and residential sectors, one may ascertain a clear representation of the relative efficiency of each state's commercial and residential energy codes.

In both sectors, it is evident that the codified minimum energy standard may vary quite significantly from one jurisdiction to another. This underscores the consideration that regardless of what ASHRAE and/or ICC may set a minimum standard for a model document, jurisdictional uptake is the most critical determinant of our nation's time horizon toward realizing net-zero energy as a minimum standard.

 

Figure 2: Commercial energy codes relative ASHRAE Standard 90.1-2019. Information was sourced from the U.S. Department of Energy and updated on March 3, 2023. Figure by Daniel Overbey. 

 

Figure 3: Residential energy codes relative 2021 IECC. Information was sourced from the U.S. Department of Energy and updated on March 3, 2023. Figure by Daniel Overbey.